Conventional recreational and commercial watercraft, for the most part, incorporate hulls which have V-shaped bottoms, with the V-shape, at its lowest point, forming a keel. The V-shape is thought to enable the boat, as speed is increased, to be pushed upwardly out of the water, as the water traversing against the boat's bow is forced sideways and downwardly at a vector to the outer shape of the hull. Such designs have been used for years, but have various deficiencies.
One detriment to such hull designs is that the draft of the boat tends to sit relatively deep in the water in relation to the length and beam of the boat, thus requiring sufficient depth of water to accommodate that draft. Another detriment to such hull designs is that they require a relatively large amount of force (and horsepower) to propel such a boat forward at a sufficient speed to stabilize the boat, i.e., to force the water sideways and downwardly as the boat travels generally horizontally through the water.
With V-shaped hull designs, initially, as velocity begins to increase from zero, the bow of the boat acts much like a plow, digging into and through the surface of the water. This creates what is known as a “bow wave”. As velocity increases more, the bow tends to be forced upwardly by the sideways and downward force being applied to the water by the curvature of the V-shape of the hull being forced horizontally forward and up over the bow wave.
Finally, when sufficient velocity is approached and then reached, the apex of the force on the V-shaped hull travels aftwardly along the hull, forcing the boat more upwardly to an increasing degree until a point is reached at which the bow, now out of the water, tends, by force of gravity, to descend toward the water, pivoting on the apex of the force against the sides and bottom of the V-shaped hull. This pivoting serves to raise the stem of the boat as the bow descends until the whole boat is lifted upwardly into what is known as a planing position. At this point, because there is relatively less water contacting the hull, drag from that water is reduced and the boat is correspondingly able to go significantly faster given the same amount of force propelling the boat forward.
Of course, as might be anticipated, the hydraulic force of the water against the V-shaped hull is substantial, and thus at least an equally substantial counteracting force must be provided by the engine of the boat. Significant power is required to get the boat up to the planing position and to maintain it there. The ultimate speed of the boat, when planing, depends on the specific design of the V-shaped hull, the weight (and weight distribution) of the boat, and the available power, i.e., the size of the engine and the size and pitch of the propeller which is driven by the engine. However, in all cases, the forward movement of the boat, at any speed, whether up on plane or not, is counteracted by both sideways and downward vectors of force produced by the relative hydraulic movement of the water against the hull.
The amount of fuel needed to power a boat at a given velocity is in direct proportion to the overall degree of each of the forces needed to be overcome to move that boat forward over a given distance. The greater those forces, the greater will be the amount of fuel consumed. Thus as a general proposition, if fuel economy is a concern, hull designs are desirable which tend to reduce the overall amount of opposing forces directed against the hull during forward movement of the boat. One approach to this is the use of relatively flat bottom hulls wherein there is less counteracting hydraulic force imposed against the hull as the boat moves forward. A flat hull is more readily pushed directly up over the bow wave to a position substantially on top of the water, creating less displacement of water by the hull in the dynamic mode as distinguished from the static mode. In other words, dynamic displacement of water is significantly less with a flat bottom boat than with a V-shaped bottom. On the other hand, static displacement, when the boat is at rest, is substantially the same for a flat bottom or a V-bottom boat, given equivalent boat weights and hull surface contact with the water.
Watercraft or boats with flat bottom hulls have been known for years. Small fishing boats have been manufactured using this design. Such boats have a relatively shallow draft to enable sports fishermen to get into shallow waters along shorelines, into shallow, swampy areas, and into lakes, ponds and streams which are not sufficiently deep to accommodate the draft of conventional V-bottom boats.
Such designs have evolved into what are popularly called “bass boats”. Bass boat hulls are relatively narrow, in relation to length, with generally flat bottoms and relatively shallow V-shapes, if any. The draft of these boats is relatively shallow in comparison to V-shaped hulls. Once up on a plane, the vector force of the water is mostly downwardly, forcing these boats to rise up out of the water to a greater degree at relatively slower speeds, thus ultimate velocity can be greater, and relatively less engine power may be required to reach a given velocity.
The down side is that, because bass boats are relatively narrow beamed and because there is relatively little sideways or lateral force being exerted against the hull of a bass boat, there is correspondingly less lateral stability, and, due to a relatively narrow beam, such boats tend to be susceptible to laterally moving waves. Such flat bottom hulls are also generally more susceptible to waves as the hull rides more on top of the waves rather than slicing somewhat through waves as V-shaped hulls do to a greater degree. Also, such boats do not steer as easily or as precisely as those with distinct, V-shaped hulls, due again to the fact that such boats incur relatively less opposing sideways forces, being those forces which tend to hold a boat to a straight forward movement. Such forces if present can be precisely altered by a rudder device at the stem. Therefore, when steered to turn, bass boats tend to skid laterally sideways more readily, thus making turning a much less precise and controllable skidding action, rather than the positive, more precisely controllable action of V-shaped hulls. Bass boat designs rarely incorporate sponsons, thus, for the sake of safety, it is almost necessary to slow some high-powered bass boats down before turning, to both effect a more precise turn and to prevent the boat from flipping over.
Both types of hulls are susceptible to wave action and may produce instability depending on the height and direction of waves. Both types of hulls have large surfaces which absorb the force of waves, and cause significant vibration, vertical or lateral movement, or a combination of these. Other boats include hull designs which incorporate pontoons or sponsons for lateral stability and floatation, but such systems are undesirable for a number of reasons.
There is thus a need for a watercraft that overcomes the deficiencies of the prior art, and efficiently maneuverable in the water, while providing increased fuel efficiency and a smooth, stable ride, even in rough water.